Department of Mechanical Engineering, Boston University, Boston, Massachusetts 02215, USA.
J Surg Res. 2011 Dec;171(2):434-42. doi: 10.1016/j.jss.2010.04.007. Epub 2010 May 20.
Temporary cold storage is a common procedure for preserving tissues for a short time before using them in a clinical or experimental setting. The process of storing tissues at refrigeration or freezing temperatures can affect the mechanical properties of the tissue. Previous studies were limited to uniaxial tensile tests and did not have substantial explanations for what was structurally occurring in the tissue to account for the changes in mechanical properties.
This study involved biaxial tensile testing of bovine thoracic aortas that had been stored at common storage temperatures (4°C, -20°C, or -80°C) for three different time points (48 h, 1 wk, or 3 wk). The slopes of the initial and stiff region of the stress-strain curves were measured. The knee point of the stress-strain curves was also determined. Collagen content before and after storage was quantified using a Sircol collagen assay kit.
The stored arteries showed decreased initial slope and increased stiff slope after 48 h of 4°C refrigeration. The -20°C and -80°C storage conditions had similar initial slopes compared with the fresh ones but an increase in the stiff slope. There was also a significant shift of the knee point to a higher strain and stress. The soluble and insoluble collagen content decreased significantly due to storage but the percentage of cross-linked collagen was unchanged.
Cold storage causes several changes in the mechanical properties due to structural and biochemical changes in the tissue. Overall, freezing protocols (either -20°C or -80°C) are suggested over refrigeration (4°C) for maintaining the initial stress-strain behavior.
在将组织用于临床或实验环境之前，短期冷藏是保存组织的常见程序。将组织储存在冷藏或冷冻温度下的过程会影响组织的机械性能。以前的研究仅限于单轴拉伸测试，并且没有对组织中发生的结构变化进行大量解释，以说明机械性能的变化。
本研究涉及对冷藏（4°C）、-20°C 和-80°C 三种常见储存温度下储存的牛胸主动脉进行双轴拉伸测试，储存时间分别为 48 小时、1 周和 3 周。测量了初始和硬区的斜率。还确定了应力-应变曲线的拐点。使用 Sircol 胶原测定试剂盒定量测量储存前后的胶原含量。
冷藏 48 小时后，储存的动脉显示初始斜率降低，硬区斜率增加。-20°C 和-80°C 储存条件与新鲜条件相比具有相似的初始斜率，但硬区斜率增加。拐点也显著向更高的应变和应力转移。由于储存，可溶性和不溶性胶原含量显著降低，但交联胶原的百分比保持不变。
由于组织的结构和生化变化，冷藏会导致机械性能发生多种变化。总体而言，建议使用冷冻（-20°C 或-80°C）方案而不是冷藏（4°C）来保持初始的应力-应变行为。
